Optical waveguide array and method of manufacturing the same

ABSTRACT

A glass containing one or more of metal microparticles, semiconductor microparticles, transition metal ion, rare earth ion and anion with characteristic absorption in a wavelength region longer than 360 nm is irradiated with a pulsed laser beam condensed at a focal point preset in an inner part of the glass. The condensed irradiation induces change of a refractive index as well as decrease of characteristic absorption in the wavelength region longer than 360 nm at the focal point. Such the domain is continuously formed by relatively shifting the focal point with respect to the glass. The continuous domains serve as optical waveguides, since optical properties are greatly different between the irradiated part and the non-irradiated part.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an optical waveguide array having thestructure that a plurality of domains where characteristic absorption ina wavelength region longer than 360 nm decreases together with change ofa refractive index are continuously formed in inner parts of material,and a method of manufacturing such the optical waveguide array.

BACKGROUND OF THE INVENTION

An optical waveguide array having optical fibers installed in asubstrate is used as a means for digital and/or image data in an opticalcommunication system. A conventional optical fiber has the structurethat a core of a higher refractive index is surrounded with a claddinglayer. Due to such the structure, incident light which is emitted to theoptical fiber with an angle less than a numerical aperture (NA) repeatstotal reflection at an interface between the core and the claddinglayer, to transmit image data toward an outlet of the optical fiber.

However, light which is emitted to the optical waveguide array with anincidence angle greater than a value corresponding to the numericalaperture (NA) does not perform total reflection at the interface betweenthe core and the cladding layer, but travels through the cladding layerto an adjacent optical fiber. Light emitted to the cladding layer alsotravels through the cladding layer and the core, and reaches theopposite side. Such the unfavorable travelling causes occurrence ofso-called “cross-talk” that the light travels in the part wheretravelling shall be originally forbidden, resulting in frequentoccurrence of errors in transmission of digital data, and decrease ofcontrast as well as degrading of image in case of transmission of imagedata.

Cross-talk is suppressed by provision of a light absorber betweenoptical fibers of an optical waveguide array to absorb leaked light, asdisclosed in JP 1-180180A and JP 3-38963A. In such an optical waveguidearray (as shown in FIGS. 1A, 1B and 1C, herein collectively referred toas FIG. 1), each core 1 a is surrounded with a cladding layer 1 b and alight-absorbing layer 1 c, a plurality of the optical fiber 1 are boundtogether as bundles 2, and each bundle 2 is individually sandwichedbetween substrates 3 such as glass. Since leaked light is separated bythe light-absorbing layer 1 c, an image is not degraded of contrastduring travelling, so that an image sensor capable of reading image datawith high resolution is offered.

However, there are restrictions on material of the light-absorbing layer1 c, since the optical fiber 1 covered with the light-absorbing layer 1c shall be good of adhesiveness to glass. In addition, a verycomplicated process is necessitated due to formation of thelight-absorbing layer 1 c as well as adhesion of bundled optical fibers1 to the substrates 3.

European Patent No. 0797112A discloses production of an opticalwaveguide by irradiation of a glass sample with a laser beam condensedat a focal point in an inner part of the glass sample to partiallyincrease a refractive index at the focal point. In this method, a quartzor fluoride glass is irradiated with a condensed laser beam to form anoptical waveguide. Production of an optical waveguide array isanticipated in course of developing such the method to enable formationof optical waveguides in an arrayed state. However, condensedirradiation with the laser beam merely induces change of an refractiveindex, but cross-talk is still unresolved. Consequently, image data aretransmitted in a degraded state with poor contrast.

SUMMARY OF THE INVENTION

The present invention aims at elimination of above-mentioned problems.An object of the present invention is to provide a new optical waveguidearray having the inner structure that a plurality of domains where achange of a refractive index as well as decrease of characteristicabsorption in a longer wavelength region occur are continuously formedby irradiating a glass, which contains an absorbing material withcharacteristic absorption in the longer wavelength, with a pulsed laserbeam condensed at a focal point preset in inner parts of the glass.

An optical waveguide array according to the present invention comprisesa glass matrix containing an absorbing material with characteristicabsorption in a wavelength region longer than 360 nm, and a plurality ofdomains, where change of a refractive index as well as decrease ofcharacteristic absorption in a wavelength longer than 360 nm occur dueto transition of the absorbing material caused by irradiation with apulsed laser beam condensed at a focal point preset in inner parts of aglass, are continuously formed in the matrix. The absorbing material maybe one or more of metal microparticles, semiconductor microparticles,transition metal ions, rare earth ions and anions.

The optical waveguide array is fabricated as follows: A pulsed laserbeam with an energy capable of inducing change of a refractive index aswell as decrease of characteristic absorption in a wavelength regionlonger than 360 nm is emitted to a glass containing an absorbingmaterial with characteristic absorption in the wavelength region longerthan 360 nm, in the manner such that a focal point of the pulsed laserbeam is adjusted to an inner part of the glass. Such irradiation iscontinued while relatively shifting the focal point in the glass, so asto form a continuous domain where change of the refractive index as wellas decrease of characteristic absorption in a wavelength region longerthan 360 nm occur in the inner part of the glass. Such the domain servesas an optical waveguide. After the focal point is relocated, the sameirradiation is repeated to form a plurality of optical waveguides.

When a glass containing an absorbing material with characteristicabsorption in a longer wavelength region is irradiated with a pulsedlaser beam condensed at a focal point preset in an inner part of theglass, change of the refractive index as well as transition of theabsorbing material occur at the focal point. Such an absorbing materialas metal microparticle, semiconductor microparticle, transition metalion, rare earth ion or anion has characteristic absorption in awavelength region longer than 360 nm. Condensed irradiation with thepulsed laser beam also changes a number of metal microparticle orsemiconductor microparticle, and a size or transformation of themicroparticle. Such the condensed irradiation also changes valence,coordination and integration of transition metal ion, rare earth ion oranion.

For instance, when a glass dispersing metal microparticles orsemiconductor microparticles therein is irradiated with a condensedpulsed laser beam, the microparticles are decreased in number, reducedin size, or dissolved or ionized in a glass matrix.

Absence of the microparticles due to such dissolution or ionizationcauses decrease of an absorption coefficient to the same value as thatof a glass free from dispersion of the microparticles, compared with alevel before irradiation. Change of the microparticles in size causeschange of absorption wavelength, i.e. decrease of an absorptioncoefficient compared with a level before irradiation.

A part subjected to condensed irradiation increases its refractive indexcompared with the other part which is not subjected to condensedirradiation, due to structural re-arrangement caused by the condensedirradiation, so that structure of an optical waveguide is formed in theglass. When a laser beam for transmission of image data with wavelengthadjusted to a wavelength region of characteristic absorption is emittedto the processed glass, the laser beam travels along the opticalwaveguide at a high efficiency, since an absorption coefficient isdecreased at the focal point while the other part keeps its originalabsorption coefficient before the condensed irradiation. In addition,light leaked out of the waveguide (the irradiated part) is trapped inthe non-irradiated part, so as to inhibit occurrence of errors in datatransmission. Consequently, image data can be read out with highresolution without degrading of contrast.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a conventional optical fiberarray.

FIG. 2 is a view for explaining irradiation of a glass havingcharacteristic absorption in a wavelength region longer than 360 nm witha pulsed laser beam condensed at a focal point preset in an inner partof the glass.

FIG. 3A is a perspective view illustrating an optical waveguide array inExample of the present invention.

FIG. 3B is a sectional view illustrating the same optical waveguidearray.

FIG. 4 is a schematic view illustrating an optical waveguide arrayhaving the structure that a plurality of domains where change of anrefractive index as well as decrease of characteristic absorption in awavelength region longer than 360 nm occur are continuously formed in aglass with characteristic absorption in the wavelength region longerthan 360 nm.

FIG. 5 is a schematic view illustrating an optical waveguide arrayhaving the structure that a plurality of domains where change of arefractive index occurs are continuously formed in a glass withoutcharacteristic absorption in a wavelength region longer than 360 nm.

FIG. 6A is a graph showing a absorption spectrum of a glass dispersingAu microparticles therein at a part irradiated with a condensed laserbeam in comparison with a non-irradiated part.

FIG. 6B is a graph showing a absorption spectrum of a glass dispersingCu microparticles therein at a part irradiated with a condensed laserbeam in comparison with a non-irradiated part.

FIG. 6C is a graph showing a absorption spectrum of a glass dispersingAg microparticles therein at a part irradiated with a condensed laserbeam in comparison with a non-irradiated part.

PREFFERED EMBODIMENT OF THE PRESENT INVENTION

Metal microparticles to be dispersed in a glass for an optical waveguidearray may be Au, Ag, Cu or Pt. Semiconductor microparticles may be CdS,CdSe, CdTe, CuCl, CuBr, ZnS or ZnSe. These microparticles may bedispersed solely or combinatively in a glass.

Condensed irradiation of a glass containing transition metal ion, rareearth ion or anion with a pulsed laser beam induces change of ionvalence, a coordination state, an integrated state and so on.Characteristic absorption before the irradiation is eliminated ordecreased due to such change. The condensed irradiation with the pulsedlaser beam forms such the optical waveguide structure, that a refractiveindex at the irradiated part is higher than a value at thenon-irradiated part, in an inner part of the glass. Travelling of alight signal along the optical wave guide (the irradiated part) isperformed with a high efficiency, and occurrence of errors in datatransmission is prevented by trapping a beam leaked out of the opticalwaveguide in the non-irradiated part. Consequently, an optical devicecapable of reading image data with high resolution without degrading ofcontrast is offered.

One or more of Cu²⁺, V³⁺, V⁴⁺, Ti³⁺, Ni²⁺, Co²⁺, Fe²⁺, Fe³⁺, Mn²⁺, Mn³⁺,Cr³⁺, Cr⁶⁺ and Mo⁴⁺ may be included as transition metal ion in a glass.One or more of Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺,Ce³⁺, Sm²⁺, Eu²⁺ and Yb²⁺ may be included as rare earth ion in theglass. One or more of OH⁻, O²⁻ and F⁻ may be included as anion in theglass.

A waveguide is formed by emitting a pulsed laser to a glass containingan absorbing material with characteristic absorption in a wavelengthregion longer than 360 nm in the manner such that a focal point of thepulsed laser beam is preset in an inner part of the glass, andrelatively shifting the focal point in the inner part of the glass so asto form a continuous domain where change of a refractive index as wellas decrease of characteristic absorption in the wavelength longer than360 nm occur. If a glass containing an absorbing material withcharacteristic absorption in a wavelength region shorter than 360 nm isirradiated with a pulsed laser beam on the contrary, leaked signal lightof wavelength generally longer than 360 nm would not be absorbed innon-irradiated glass matrix resulting cross-talk. Furthermore, decreaseof the characteristic absorption effective for a waveguide is hardlyrealized since the glass itself often has characteristic absorption inthe wavelength region shorter than 360 nm. However, a glass containingan absorbing material may be available for fabrication of an opticalwaveguide array, as far as condensed irradiation with a pulsed laserbeam induces decrease of characteristic absorption of the absorbingmaterial in a wavelength region longer than 360 nm, with the provisothat a tail of the absorption overlaps a wavelength region longer than360 nm even if a peak of characteristic absorption is shorter than 360nm and that the glass containing such the absorbing material has ahigher absorption coefficient in a wavelength region longer than 360 nmcompared with a glass which does not contain such the absorbingmaterial.

A pulsed laser beam with an energy sufficient for inducing change of arefractive index as well as decrease of characteristic absorption in awavelength region longer than 360 nm is used for formation of awaveguide, although the energy depends on a kind of a glass. A peakpower of the pulsed laser beam is represented by a power (W) which is avalue of an output energy (J) per one pulse divided by pulse width(second), and a peak powder density is represented by a value(W/cm²) ofa peak power per a unit area (cm²).

A peak power density is preferably within a range of 10⁵-10¹⁵ W/cm² at afocal point in order to induce change of a refractive index as well asdecrease of characteristic absorption in a wavelength region longer than360 nm. If the peak power density is less than 10⁵ W/cm², change of arefractive index and decrease of characteristic absorption in awavelength region longer than 360 nm hardly occur at the focal point. Ifthe peak power density exceeds 10¹⁵ W/cm² on the contrary, change of arefractive index as well as decrease of characteristic absorption in awavelength region longer than 360 nm unfavorably occur at the other partexcept the focal point. Besides, it is practically difficult to emit alaser beam with an excessively big energy.

When a glass is irradiated with a pulsed laser beam with the same peakpower density, the possibility to induce change of a refractive index aswell as decrease of characteristic absorption in a wavelength regionlonger than 360 nm is intensified as narrower pulse width of the pulsedlaser beam. In this sense, narrower pulse width is better, and ispreferably 10⁻¹⁶ second or shorter. If a glass is irradiated with apulsed laser beam with too wider pulse width, emission of a pulsed laserbeam with an excessively big energy is necessitated in order to gain thesimilar peak power density as that of a pulsed laser beam with narrowerpulse width. Application of such the big energy causes fracture of theglass. If a glass is irradiated with a pulsed laser beam with wavelengthin an absorption wavelength region of the glass, intensity of the pulsedlaser beam becomes weaker as the pulsed laser beam travels in the glassalong its depth direction. However, any special restrictions are not puton wavelength of a pulsed laser beam, as far as an energy with apredetermined peak power density is applied to a part of a glass whichis expected to form an optical waveguide.

A pulsed laser beam with narrower pulse width, i.e. a greater repetitionrate is preferable for formation of a smooth waveguide structure, so asto apply a first pulse and then a second pulse in a possible shortesttime period. In this sense, a repetition rate of a pulsed laser beam is10 kHz or more (preferably 100 kHz or more).

A pulsed laser beam with too small repetition rate is discretely emittedto a glass without induction of change of a refractive index necessaryfor formation of a continuous optical waveguide. A glass can besubjected to continuous irradiation with a pulsed laser beam by loweringa relative velocity of a glass or a focal point. However, since a secondpulse is applied in an overlapping state after lapse of a predeterminedtime period from application of a first pulse, a part where the firstpulse induced change of a refractive index would be unfavorably deformedby application of the second pulse. Such deformation causes ruggedstructure of an optical waveguide.

An upper limit of a repetition rate is indefinite, and a pulsed laserbeam limitlessly similar to continuous light may be used. However, anenergy per one pulse becomes weaker as increase of a repetition rate .In this sense, the upper limit of the repetition rate is practicallydetermined accounting a threshold which induces change of a refractiveindex in a glass as well as decrease of characteristic absorption in awavelength region longer than 360 nm in comparison with an output of apulsed laser beam to be emitted.

When a glass with characteristic absorption in a wavelength regionlonger than 360 nm is irradiated with a pulsed laser beam in the mannersuch that a focal point of the pulsed laser beam is preset in an innerpart of the glass, a quantity of light necessary for inducing change ofa refraction index as well as transition of an absorbing material (i.e.the characteristic absorption cause) is not gained at the other partexcept the focal point. Consequently, change of a refractive index aswell as decrease of characteristic absorption in a wavelength regionlonger than 360 nm selectively is limited to the focal point, while theglass keeps its original refractive index and an original state of theabsorbing material at the other part except the focal point (anon-irradiated part). Due to such selective reformation, an opticalwaveguide structure is formed in an inner part of the glass.

A pulsed laser beam 5 emitted from a light source is condensed by acondenser lens 8 or the like so as to position its focal point 6 at aninner part of a glass 7, as shown in FIG. 2. A domain where change of arefractive index as well as decrease of characteristic absorption in awavelength region longer than 360 nm occur is continuously formed in theinner part of the glass 7, by relatively shifting the focal point 6 inthe glass 7. Relative movement of the focal point 6 with respect to theglass 7 may be performed by continuously shifting the glass 7 withrespect to the focal point 6 of the pulsed laser beam 5, continuouslyshifting the focal point in the glass 7, or shifting both the focalpoint 6 and the glass 7.

Since the domain where change of a refractive index as well as decreaseof characteristic absorption occur is continuously formed in the innerpart of the glass 7, such the domain serves as an optical waveguide 11(as shown in FIG. 3). A core diameter of the optical waveguide 11 iscontrolled by the focal distance of the condenser lens 6.

A glass substrate 7 with characteristic absorption in a wavelengthregion longer than 360 nm is used for fabrication of an opticalwaveguide array having a profile shown in FIG. 3A and a cross sectionshown in FIG. 3B.

A first optical waveguide 11 is formed in a first step wherein a focalpoint 6 of a pulsed laser beam 5 is relatively shifted in an inner partof a glass 7. The focal point 6 is then relocated to another positiondifferent from an initial point of the first optical waveguide 11 andshifted in the inner part of the glass 7 along a direction parallel tothe first optical waveguide 11, to form a second optical waveguide 12 ina second step. Relocation and shifting of the focal point 6 are repeatedthereafter in the same way to form an optical waveguide array 10comprising a plurality of optical waveguides indicated by 11 and 12.parallel together. The inner part (irradiated part) of the glass 7 wherethe optical waveguides 11 and 12 . . . are formed changes its refractiveindex and decrease of characteristic absorption in a wavelength regionlonger than 360 nm, while the other part 19 (non-irradiated part) keepsits original refractive index without decrease of characteristicabsorption.

When a laser beam for transmission of image data with wavelengthpredetermined in a wavelength region corresponding to characteristicabsorption of the non-irradiated part 19 (glass matrix) is emitted tothe waveguide array 10, the incident beam travels through the opticalwaveguides 11 and 12 . . . with high performance, since an absorptioncoefficient at the irradiated part (corresponding to the focal point 6)is decreased while the non-irradiated part 19 keeps its originalabsorption coefficient. The laser beam leaked out of the opticalwaveguides 11 and 12 . . . is trapped in the non-irradiated part 19. Asa result, the image data can be read out with high resolution withoutoccurrence of cross-talk which causes data errors or degrading ofcontrast.

EXAMPLE 1 Fabrication of an Optical Waveguide Array From a GlassDispersing Au Microparticles Therein

SiO₂, B₂O₃, Na₂CO₃ and Sb₂O₅ raw materials were weighed and mixedtogether, and an aqueous chloroauric acid solution was added to thepowdery mixture to prepare glass composition of 72 parts by weight SiO₂,18 parts by weight B₂O₃, 10 parts by weight Na₂O, 4 parts by weightSb₂O₃ and 0.02 parts by weight Au.

The powdery mixture (400 g) was put in a Pt crucible of 300 cc capacity,and melted under tilting condition 2 hours at 1450° C. in the open air.Uniform glass melt was shaped to a sheet of 5 mm in thickness by moldingit in a brass die, and then cooled. The glass sheet obtained wasannealed at 450° C. to release strains.

The glass sheet was set in an electric oven, heated at 5° C./minute,held 8 hours at 700° C., and then cooled as such in the oven toprecipitate Au microparticles in the glass. The glass was colored todark-red due to precipitation of Au microparticles. After theheat-treated glass was trimmed and ground, a parallelepiped sample of 10mm in length, 10 mm in width and 2 mm in thickness was cut off the glasssheet.

The sample was examined by absorption spectrum analysis. Itspermeability to light of wavelength shorter than 580 nm was 0%.

The glass sample 7 was mounted on an electromotive stage capable ofmoving along X, Y and Z directions, and irradiated with a pulsed laserbeam 5 in the manner such that a focal point 6 of the pulsed laser beam5 was adjusted to an inner part of the glass sample 7 by a condenserlens 8. The focal point 6 was shifted with respect to the glass sample 7along the Z direction (corresponding to an optical axis of the laserbeam 5), without movement of the focal point 6 along the X and Zdirections. A pulsed laser beam 5 (800 nm wavelength, pulse width of1.5×10⁻¹³ second, a repetition rate of 200 kHz and an averaged power of500 mW) oscillated from a Ti-sapphire laser excited with an argon laserwas used as the pulsed laser beam 5.

Increase of a refractive index by 0.01 at the focal point 6 wasrecognized by observation of the irradiated glass sample 5. Change of arefractive index as well as decrease of characteristic absorption in awavelength region longer tan 360 nm occurred in a very short time periodof nanosecond or picosecond order.

The glass sample 7 and/or the focal point 6 were relatively shiftedalong the Z direction (an optical axis) to form a straight domain (i.e.a first optical waveguide 11) with an increased refractive index wasformed in an inner part of the glass sample 7.

Formation of the optical waveguide 11 was confirmed by actually emittinga laser beam of 800 nm wavelength to the glass sample 7 and detectingtravel of the laser beam only through the domain where change of arefractive index occurred. A near-field image at the outlet side provedthat the optical guide wave 11 had cross section of 15 μm in diameter(core diameter). FIG. 6A shows a measurement result of absorptionspectrum of the optical waveguide 11. It is noted from FIG. 6A that theoptical waveguide 11 was defined by a domain where an absorptioncoefficient in a wavelength region of approximately 580-400 nm caused byAu microparticles decreased and dark-red disappeared. On the other hand,change of permeability was not detected at the non-irradiated part 19.

A core diameter of the optical waveguide 11 was controlled by changing afocal distance of the condenser lens 8. In the case where the glasssample 7 was irradiated with another pulsed laser beam of differentwavelength (e.g. 1.3 μm or 1.55 μm in a wavelength region for commercialcommunication) instead of the pulsed laser beam 5 of 800 nm, the samechange of a refractive index as well as the same decrease ofcharacteristic absorption in a wavelength longer than 360 nm were alsodetected.

After the glass sample 7 was shaded from irradiation with the pulsedlaser beam 5, the glass sample 7 and/or the focal point 6 wererelocated. The glass sample 7 and/or focal point 6 were then shiftedalong a direction in parallel to the first optical waveguide 11, to forma second optical waveguide 12. Relocation and shifting of the glasssample 7 and/or the focal point 6 were repeated to fabricate an opticalwaveguide array 10 having the structure that a plurality of opticalwaveguides such as those indicated by 11 and 12 . . . are arranged inparallel together and surrounded with a non-irradiated part 19 whichkept its original refractive index without change of characteristicabsorption.

The optical waveguide array 10 obtained in this way was examined by atest to research read-out contrast using a laser beam of 550 nmwavelength. It was confirmed that the optical waveguide array performedextremely high contrast without cross talk, compared with an opticalwaveguide array which was fabricated using change of a refractive indexonly in under-mentioned Comparative Example 1.

EXAMPLE 2 Fabrication of an Optical Waveguide Array From a GlassDispersing Cu Microparticles Therein

SiO₂, B₂O₃, Na₂CO₃, Cu₂O, SnO raw materials were weighed and mixedtogether to prepare glass composition of 72 parts by weight SiO₂, 20parts by weight B₂O₃, 8 parts by weight Na₂O, 0.5 parts by weight Cu and0.25 parts by weight SnO.

The powdery mixture (400 g) was melted with a heat and shaped to a sheetof 6 mm in thickness by the same way as Example 1. The glass sheet wasannealed at 450° C. to release strains. The annealed glass sheet was setin an electric oven, heated at 5° C./minute, held 4 hours at 650° C.,and then cooled as such in the oven to precipitate Cu microparticles ina glass matrix. The glass sheet was colored to red due to precipitationof Cu microparticles. After the heat-treated glass sheet was trimmed andground, a sample of 10 mm in length, 10 mm in width and 4 mm inthickness was cut off the glass sheet.

The sample was examined by absorption spectrum analysis. Itspermeability to light of wavelength shorter than 620 nm was 0%.

The glass sample 7 was irradiated with a condensed pulsed laser beam 5by the same way as Example 1. Increase of a refractive index by 0.01 atthe focal point 6 was detected by observation of the irradiated glasssample 7. Decrease of characteristic absorption in a wavelength regionlonger than 360 nm was also noted in Example 2, regardless very shortirradiation of nanosecond or picosecond order. A straight opticalwaveguide 11 was formed in an inner part of the glass sample 7 bycontinuously shifting the glass sample 7 and/or the focal point 6 alongthe Z direction (an optical axis).

A near-field image at an outlet side proved that the formed opticalwaveguide 11 had cross section of 15 μm in diameter (core diameter).FIG. 6B shows a measurement result of absorption spectrum of the opticalwaveguide 11. FIG. 6B proves formation of a domain where an absorptioncoefficient in a wavelength region of approximately 620-400 nm caused byCu microparticles decreased and red color disappeared. On the otherhand, change of permeability was not detected at the non-irradiated part19.

Second and following optical waveguides indicated by 12 . . . wereformed by the same way as Example 1 after formation of the first opticalwaveguide 11, to fabricate an optical waveguide array (shown in FIG. 4)having the structure that a plurality of optical waveguides indicated by11 and 12 . . . were arranged in parallel together and surrounded withthe non-irradiated part 19 which kept its original refractive indexwithout decrease of characteristic absorption. The optical waveguidearray 10 obtained in this way was examined by a test to researchread-out contrast using a laser beam of 530 nm wavelength. It wasconfirmed that the optical waveguide array performed extremely highcontrast, compared with an optical waveguide array (under-mentionedComparative Example 1) which was fabricated using change of a refractiveindex only.

EXAMPLE 3 Fabrication of an Optical Waveguide Array From a GlassDispersing Ag Mircroparticles Therein

SiO₂, CaCO₃, Na₂CO₃, Ag₂O, SnO raw materials were weighed and mixed toprepare glass composition of 72 parts by weight SiO₂, 20 parts by weightCaO, 8 parts by weight Na₂O, 0.4 parts by weight Ag, 0.2 parts by weightSnO.

The powdery mixture (400 g) was put in a Pt crucible of 300 cc capacityand melted under a tilting condition 2 hours at 1450° C. in the openair.

Uniform glass melt was molded to a sheet by the same way as Example 1.The glass sheet was set in an electric oven, heated at 5° C./minute,held 4 hours at 550° C. and then cooled as such in the oven toprecipitate Ag microparticles. The glass sheet was colored to yellow dueto precipitation of Ag microparticles. After the heat-treated glasssheet was trimmed and ground, a glass sample of 10 mm in length, 10 mmin width and 3 mm in thickness was cut of the glass sheet.

The glass sample was examined by absorption spectrum analysis. Itspermeability to a laser beam of wavelength shorter than 420 nm was 0%.

The glass sample 7 was irradiated with a condensed pulsed laser beam 5by the same way as Example 1. Increase of a refractive index by 0.01 atthe focal point 6 was recognized by observation of the irradiated glasssample 7. A straight optical waveguide 11 was formed in an inner part ofthe glass sample 7 by relative movement of the glass sample 7 or thefocal point 6 along one direction. Change of a refractive index at thefocal point 6 as well as decrease of characteristic absorption were alsoperformed in a very short time period of nanosecond or picosecond order.

Formation of the optical waveguide 11 was recognized by actuallyemitting a laser beam of 800 nm wavelength and observing travel of thelaser beam only through a domain where change of a refractive indexoccurred. A near-field image proved that the optical waveguide 11 hadcross section of 15 μm in diameter (core diameter). FIG. 6C shows ameasurement result of absorption spectrum of the optical waveguide 11.Decrease of an absorption coefficient in a wavelength region ofapproximately 420-360 nm caused by Ag microparticles is noted in FIG.6C, and such the domain was not tinged with yellow. On the other hand,change of permeability was not detected at the non-irradiated part 19.

Second and following optical waveguides indicated by 12 . . . wereformed in parallel to the first optical waveguide 11 by the same way asExample 1, to fabricate an optical waveguide array. The opticalwaveguide array was examined by a test to research read-out contrastusing a laser beam of 420 nm. As a result, the optical waveguide arrayperformed extremely high contrast, compared with an optical waveguidearray (under-mentioned Comparative Example 2) array using change of arefractive index only.

EXAMPLE 4 Fabrication of an Optical Waveguide Array From a GlassDispersing Pt Microparticles Therein

SiO₂, B₂O₃, Na₂CO₃ and Sb₂O₃ raw materials were weighed and mixedtogether, and an aqueous platinic chloride solution was added to thepowdery mixture to prepare glass composition of 72 parts by weight SiO₂,18 parts by weight B₂O₃, 10 parts by weight Na₂O, 2 parts by weightSb₂O₃ and 0.05 parts by weight Pt.

The powdery mixture (400 g) was put in a Pt crucible and melted under atilting condition 2 hours at 1450° C. in the open air. Uniform glassmelt was molded to a glass sheet by the same way as Example 1. The glasssheet was set in an electric oven, heated at 5° C./minute, held 4 hoursat 600° C. and then cooled as such in the oven to precipitate Ptmicroparticles. The glass sheet was colored to gray due to precipitationof Pt microparticles. After the glass sheet was trimmed and ground, asample of 10 mm in length, 10 mm in width and 4 mm thickness was cut offthe glass sheet.

The glass sample was examined by absorption spectrum analysis. Itspermeability to visible light of 750-400 nm is at a relatively low levelof 20% in average.

The glass sample 7 was then irradiated with a condensed pulsed laserbeam 5 by the same way as Example 1. Increase of a refractive index by0.01 at the focal point 6 was recognized by observation of theirradiated glass sample 7. A straight optical waveguide 11 was formed inan inner part of the glass sample 7 by relative movement of the glasssample 7 or the focal point 6 along one direction. Change of arefractive index at the focal point 6 as well as decrease ofcharacteristic absorption were performed in a very short time period ofnanosecond or picosecond order, also in this case.

Formation of the optical waveguide 11 was recognized by actuallyemitting a laser beam of 800 nm wavelength to the glass sample 7 andobserving travel of the laser beam only through a domain where change ofa refractive index occurred. A near-field image proved that the opticalwaveguide 11 had cross section of 15 μm in diameter (core diameter).Decrease of an absorption coefficient in a wavelength region ofapproximately 750-400 nm caused by Pt microparticles was recognized froma measurement result of absorption spectrum, and such the domain was nottinged with gray. On the other hand, change of permeability was notdetected at the non-irradiated part 19.

Second and following optical waveguides indicated by 12 . . . wereformed in parallel to the first optical waveguide 11 by the same way asExample 1, to fabricate an optical waveguide array (shown in FIG. 4).The optical waveguide array was examined by a test to research read-outcontrast using a laser beam of 600 nm wavelength. As a result, theoptical waveguide performed extremely high contrast, compared with anoptical waveguide (under-mentioned Comparative Example 2) array usingchange of a refractive index only.

EXAMPLE 5 Fabrication of an Optical Waveguide Array From a GlassDispersing CuCl Microparticles Therein

SiO₂, Al₂O₃, B₂O₃, Li₂CO₃, Na₂CO₃, K₂CO₃, CuCl and SnO raw materialswere weighed and mixed together, to prepare glass composition of 65parts by weight SiO₂, 6 parts by weight Al₂O₃, 17 parts by weight Ba₂O₃,4 parts by weight Li₂O, 4 parts by weight Na₂O, 4 parts by weight K₂O,0.5 parts by weight CuCl and 0.2 parts by weight SnO.

The powdery mixture (400 g) was put in a Pt crucible of 300 cc capacityand melted under a tilting condition 2 hours at 1450° C. in the openair. Uniform glass melt was molded to a glass sheet by the same way asExample 1. The glass sheet was set in an electric oven, heated at 5°C./minute, held 4 hours at 550° C. and then cooled as such in the ovento precipitate CuCl microparticles. After the glass sheet was trimmedand ground, a glass sample of 10 mm in length, 10 mm in width and 4 mmthickness was cut off the glass sheet.

The glass sample was examined by absorption spectrum analysis. Itspermeability to light of wavelength shorter than 380 nm was 0%.

The glass sample 7 was then irradiated with a condensed pulsed laserbeam 5 by the same way as Example 1. Increase of a refractive index by0.01 at the focal point 6 was recognized by observation of theirradiated glass sample 7. A straight optical waveguide 11 was formed inan inner part of the glass sample 7 by relative movement of the glasssample 7 or the focal point 6 along one direction. Change of arefractive index at the focal point 6 as well as decrease ofcharacteristic absorption were performed in a very short time period ofnanosecond or picosecond order, also in this case.

Formation of the optical waveguide 11 was recognized by actuallyemitting a laser beam of 800 nm wavelength to the glass sample 7 andobserving travel of the laser beam only through a domain where change ofa refractive index occurred. A near-field image at an outlet side provedthat the optical waveguide 11 had cross section of 15 μm in diameter(core diameter). Decrease of an absorption coefficient in a wavelengthregion of approximately 360-380 nm caused by CuCl microparticles wasrecognized from a measurement result of absorption spectrum. On theother hand, change of permeability was not detected at thenon-irradiated part 19.

The same change of a refractive index as well as the same decrease ofcharacteristic absorption in a wavelength region longer than 360 nm werealso detected, when the glass sample 7 was irradiated with a secondharmonic of 400 nm wavelength or a laser beam of 1.3 μm or 1.55 μm in awavelength region for commercial transmission instead of the laser beamof 800 nm wavelength.

Second and following optical waveguides indicated by 12 . . . wereformed in parallel to the first optical waveguide 11 by the same way asExample 1, to fabricate an optical waveguide array (shown in FIG. 4).The optical waveguide array was examined by a test to research read-outcontrast using a laser beam of 380 nm. As a result, the opticalwaveguide array performed extremely high contrast, compared with anoptical waveguide array (under-mentioned Comparative Example 3) usingchange of a refractive index only.

EXAMPLE 6 Fabrication of an Optical Waveguide From a Glass ContainingCo²⁺ Ion

SiO₂, B₂O₃, Na₂O₃ and CoO raw materials were weighed and mixed togetherto prepare glass composition of 72 parts by weight SiO₂, 20 parts byweight B₂O₃, 8 parts by weight Na₂O and 0.05 parts by weight CoO. Thepowdery mixture (400 g) was put in a Pt crucible of 300 cc capacity, andmelted under a tilting condition 2 hours at 1450° C. in the open air.Uniform glass melt was poured in a brass die and shaped to a sheet of 6mm in thickness. After the glass sheet was cooled, it was annealed at450° C. to release strains. After the annealed glass sheet was trimmedand ground, and a glass sample of 10 mm in length, 10 mm in width and 2mm in thickness was cut off the glass sheet.

The glass sample was examined by absorption spectrum analysis. Itspermeability to light of 550-700 nm was 0% due to inclusion of Co²⁺which had an absorption band in a wavelength region of 550-700 nm.

The glass sample 7 was then irradiated with a condensed pulsed laserbeam 5 by the same way as Example 1. Increase of a refractive index by0.01 at the focal point 6 was recognized by observation of theirradiated glass sample 7. A straight optical waveguide 11 was formed inan inner part of the glass sample 7 by relative movement of the glasssample 7 or the focal point 6 along one direction. Change of arefractive index at the focal point 6 as well as decrease ofcharacteristic absorption were performed in a very short time period ofnanosecond or picosecond order, also in this case.

Formation of the optical waveguide 11 was recognized by actuallyemitting a laser beam of 800 nm wavelength to the glass sample 7 andobserving travel of the laser beam only through a domain where change ofa refractive index occurred. A near-field image at an outlet side provedthat the optical waveguide 11 had cross section of 15 μm in diameter(core diameter). Decrease of an absorption coefficient in a wavelengthregion of approximately 700-550 nm caused by Co²⁺ ion was recognizedfrom a measurement result of absorption spectrum, and the domain was nottinged with blue. On the other hand, change of permeability was notdetected at the non-irradiated part 19.

Second and following optical waveguides indicated by 12 . . . wereformed in parallel to the first optical waveguide 11 by the same way asExample 1, to fabricate an optical waveguide array (shown in FIG. 4).The optical waveguide array was examined by a test to research read-outcontrast using a laser beam of 650 nm wavelength. The optical waveguidearray performed extremely high contrast, compared with an opticalwaveguide array (under-mentioned Comparative Example 1) using change ofa refractive index only.

EXAMPLE 7 Fabrication of an Optical Waveguide Array From a GlassContaining Ni²⁺ ion

So₂, B₂O₃, Na₂O₃ and NiO raw materials were weighed and mixed togetherto prepare glass composition of 72 parts by weight SiO₂, 20 parts byweight B₂O₃, 8 parts by weight Na₂O, 0.2 parts by weight NiO. Thepowdery mixture (400 g) was put in a Pt crucible of 300 cc capacity, andmelted under a tilting condition 2 hours at 1450° C. in the open air.Uniform glass melt was poured in a Pt die and shaped to a sheet by thesame way as Example 6. After the glass sheet was trimmed and ground, aglass sample of 10 mm in length, 10 mm in width and 5 mm in thicknesswas cut off the glass sheet.

The glass sample was examined by absorption spectrum analysis. Itspermeability to light of 450-550 nm was 0% due to inclusion of Ni²⁺which had an absorption band in a wavelength region of 450-550 nm.

The glass sample 7 was then irradiated with a condensed pulsed laserbeam 5 by the same way as Example 1. Increase of a refractive index by0.01 at the focal point 6 was recognized by observation of theirradiated glass sample 7. A straight optical waveguide 11 was formed inan inner part of the glass sample 7 by relative movement of the glasssample 7 or the focal point 6 along one direction. Change of arefractive index at the focal point 6 as well as decrease ofcharacteristic absorption were performed in a very short time period ofnanosecond or picosecond order, also in this case.

Formation of the optical waveguide 11 was recognized by actuallyemitting a laser beam of 800 nm wavelength to the glass sample 7 andobserving travel of the laser beam only through a domain where change ofa refractive index occurred. A near-field image at an outlet side provedthat the optical waveguide 11 had cross section of 15 μm in diameter(core diameter). Decrease of an absorption coefficient in a wavelengthregion of approximately 650-450 nm caused by Ni²⁺ ion was recognizedfrom a measurement result of absorption spectrum, and the domain was nottinged with brown. On the other hand, change of permeability was notdetected at the non-irradiated part 19.

Second and following optical waveguides 12 . . . were formed in parallelto the first optical waveguide 11 by the same way as Example 1, tofabricate an optical waveguide array (shown in FIG. 4). The opticalwaveguide array was examined by a test to research read-out contrastusing a laser beam of 550 nm wavelength. The optical waveguide arrayperformed extremely high contrast, compared with an optical waveguidearray (under-mentioned Comparative Example 1) using change of arefractive index only.

EXAMPLE 8 Fabrication of an Optical Waveguide Array From a GlassContaining Pr³⁺ ion

ZrF₄, BaF₂, LaF₃, AlF₃, NaF and PrF₃ raw materials were weighed andmixed together to prepare glass composition of 53 mol % ZrF₄, 20 mol %BaF₂, 4 mol % LaF₃, 3 mol % AlF₃, 20 mol % NaF and 1 mol % PrF₃.

The powdery mixture (500 g) was put in a Pt crucible of 300 cc capacity,and melted under a tilting condition 1 hour at 900° C. in a nitrogenatmosphere. Uniform glass melt was poured in a brass die, shaped to asheet of 5 mm in thickness, and then cooled. The glass sheet obtained inthis way was annealed at 260° C. to release strains. After the annealedglass sheet was trimmed and ground, a sample of 10 mm in length, 10 mmin width and 3 mm in thickness was cut off the glass sheet.

The glass sample was examined by absorption spectrum analysis. Itspermeability to light of 450-550 nm was 5% due to inclusion of Pr³⁺which had an absorption band in a wavelength region of 450-550 nm.

The glass sample 7 was then irradiated with a condensed pulsed laserbeam 5 by the same way as Example 1. Increase of a refractive index by0.01 at the focal point 6 was recognized by observation of theirradiated glass sample 7. A straight optical waveguide 11 was formed inan inner part of the glass sample 7 by relative movement of the glasssample 7 or the focal point 6 along one direction. Change of arefractive index at the focal point 6 as well as decrease ofcharacteristic absorption were performed in a very short time period ofnanosecond or picosecond order, also in this case.

Formation of the optical waveguide 11 was recognized by actuallyemitting a laser beam of 800 nm wavelength to the glass sample 7 andobserving travel of the laser beam only through a domain where change ofa refractive index occurred. A near-field image at an outlet side provedthat the optical waveguide 11 had cross section of 15 μm in diameter(core diameter). Decrease of an absorption coefficient in a wavelengthregion of approximately 550-450 nm caused by Pr³⁺ ion was recognizedfrom a measurement result of absorption spectrum, and the domain was nottinged with yellowish green. On the other hand, change of permeabilitywas not detected at the non-irradiated part 19.

Second and following optical waveguides 12 . . . were formed in parallelto the first optical waveguide 11 by the same way as Example 1, tofabricate an optical waveguide array (shown in FIG. 4). The opticalwaveguide array was examined by a test to research read-out contrastusing a laser beam of 500 nm wavelength. The optical waveguide arrayperformed extremely high contrast, compared with an optical waveguidearray (under-mentioned Comparative Example 4) array using change of arefractive index only.

COMPARATIVE EXAMPLE 1

SiO₂, B₂O₃, Na₂O and Sb₂O₃ raw materials were weighed and mixed togetherto form the same glass matrix as Example 1 except absence of Au (i.e. 72parts by weight SiO₂, 18 parts by weight B₂O₃, 10 parts by weight Na₂Oand 4 parts by weight Sb₂O₃). The powdery mixture (400 g) was put in aPt crucible of 300 cc capacity, and melted under a tilting condition 2hour at 1450° C. in the open air. Uniform glass melt was poured in abrass die, shaped to a sheet of 5 mm in thickness, and then cooled. Theglass sheet obtained in this way was annealed at 450° C. to releasestrains. After the annealed glass sheet was trimmed and ground, a glasssample of 4 mm thickness was cut off the glass sheet.

The glass sample was irradiated with a condensed pulsed laser beam underthe same conditions as Example 1, to form an optical waveguide in aninner part of the glass sample.

Formation of a domain 21 (shown in FIG. 5) where change of a refractiveindex occurred was recognized by observation of the irradiated glasssample. Such the change of a refractive index was not detected at anon-irradiated part 29. A plurality of optical waveguides were formed inthe same way as Example 1, to fabricate an optical waveguide array. Theoptical waveguide array was examined by a test to research read-outcontrast using light of 550 nm. Due to cross talk, the read-out contrastwas very weak compared with Example 1, since change of a refractiveindex only was effective for read-out without decrease of characteristicabsorption derived from valence change of Au.

COMPARATIVE EXAMPLE 2

SiO₂, CaCO₃, Na₂CO₃ and SnO raw materials were weighed and mixedtogether to form the same glass matrix as Example 3 except absence of Ag(i.e. 72 parts by weight SiO₂, 20 parts by weight CaO, 8 parts by weightNa₂O and 0.2 parts by weight SnO). The powdery mixture (400 g) was putin a Pt crucible of 300 cc capacity and melted under a tilting condition2 hour at 1450° C. in the open air. Uniform glass melt was cast to asheet by the same way as Example 3. After the glass sheet was trimmedand ground, a glass sample of 3 mm in thickness was cut off the glasssheet.

The glass sample was irradiated with a condensed pulsed laser beam underthe same conditions as Example 3, to form an optical waveguide in aninner part of the glass sample.

Formation of a domain 21 (shown in FIG. 5) where change of a refractiveindex occurred was recognized by observation of the irradiated glasssample. Such the change of a refractive index was not detected at anon-irradiated part 29. A plurality of optical waveguides were formed inthe same way as Example 3, to fabricate an optical waveguide array. Theoptical waveguide array was examined by a test to research read-outcontrast using light of 420 nm. The read-out contrast was very weakcompared with Example 3, since change of a refractive index only waseffective for read-out without decrease of characteristic absorption.

COMPARATIVE EXAMPLE 3

SiO₂, Al₂O₃, B₂O₃, LiCO₃, Na₂O₃, K₂CO₃ and SnO raw materials wereweighed and mixed together to form the same glass matrix as Example 5except absence of CuCl microparticles (i.e. 65 part by weight SiO₂, 6parts by weight Al₂O₃, 17 parts by weight B₂O₃, 4 parts by weight Li₂O,4 parts by weight Na₂O, 4 parts by weight K₂O and 0.2 parts by weightSnO). The powdery mixture (400 g) was put in a Pt crucible of 300 cccapacity, and melted under a tilting condition 2 hour at 1450° C. in theopen air. Uniform glass melt was cast to a sheet by the same way asExample 5. After the glass sheet was trimmed and ground, a glass sampleof 4 mm thickness was cut off the glass sheet.

The glass sample was irradiated with a condensed pulsed laser beam underthe same conditions as Example 5, to form an optical waveguide in aninner part of the glass sample.

Formation of a domain 21 (shown in FIG. 5) where change of a refractiveindex occurred was recognized by observation of the irradiated glasssample. Such the change of a refractive index was not detected at anon-irradiated part 29. A plurality of optical waveguides were formed inthe same way as Example 5, to fabricate an optical waveguide array. Theoptical waveguide array was examined by a test to research read-outcontrast using light of 380 nm. The read-out contrast was very weakcompared with Example 5, since change of a refractive index only waseffective for read-out without decrease of characteristic absorption.

COMPARATIVE EXAMPLE 4

High-purity ZrF₄, BaF₂, LaF₃, AlF₃ and NaF raw materials were weighedand mixed together to form the same glass matrix as Example 8 exceptabsence of PrF₃ (i.e. 53 mol % ZrF₄, 20 mol % BaF₂, 4 mol % LaF₃, 3 mol% AlF₃ and 20 mol % NaF). The powdery mixture (400 g) was put in a Ptcrucible of 300 cc capacity, and melted under a tilting condition 2 hourat 900° C. in a nitrogen atmosphere. Uniform glass melt was poured in abrass die and cast to a sheet of Smin in thickness. After the glasssheet was cooled, it was annealed at 260° C. to release strains. A glasssample of 3 mm in thickness similar to Example 8 was cut off the glasssheet.

The glass sample was irradiated with a condensed pulsed laser beam underthe same conditions as Example 8, to form an optical waveguide in aninner part of the glass sample.

Formation of a domain 21 (shown in FIG. 5) where change of a refractiveindex occurred was recognized by observation of the irradiated glasssample. Such the change of a refractive index was not detected at anon-irradiated part 29. A plurality of optical waveguides were formed inthe same way as Example 8, to fabricate an optical waveguide array. Theoptical waveguide array was examined by a test to research read-outcontrast using light of 500 nm. The read-out contrast was very weakcompared with Example 8, since change of a refractive index only waseffective for read-out without decrease of characteristic absorption.

INDUSTRIAL APPLICATION

According to the present invention as above-mentioned, a glass withcharacteristic absorption in a wavelength region longer than 360 nm isirradiated with a pulsed laser beam which is condensed at a focal pointpreset in an inner part of the glass, to form a continuous domain actingas an optical waveguide due to change of a refractive index as well asdecrease of characteristic absorption in a wavelength longer than 360nm. An optical waveguide array is fabricated by formation of a pluralityof such the waveguides. Since the optical waveguide array fabricated inthis way has the structure that the waveguides are surrounded withnon-irradiated parts capable of absorbing the leaked light and greatlydifferent in optical properties, it is used as a product with a highreliability without occurrence of cross-talk. In addition, such theoptical waveguide array can be fabricated with high productivity by asimplified process, compared with a conventional optical waveguide arrayprovided with a light-absorbing layer. Furthermore, wavelength of lightto be transmitted without cross-talk can be freely predetermined byproper selection of a glass with characteristic absorption in awavelength region longer than 360 nm.

What is claimed is:
 1. An optical waveguide array comprising a glassmatrix which contains one or more absorbing materials selected from thegroup consisting of metal microparticles, semiconductor microparticles,transition metal ion, rare earth ion and an anion, and having aplurality of domains each continuously formed in said glass matrix byirradiation with a pulsed laser beam condensed at a focal point presetin an inner part of said glass matrix to induce change of a refractiveindex as well as decrease of characteristic absorption in a wavelengthregion for the visible range.
 2. The optical waveguide array as claimedin claim 1, wherein the metal microparticles are selected from the groupconsisting of Au, Ag, Cu and Pt; the semiconductor microparticles areselected from the group consisting of CdS, CdSe, CdTe, CuCl, CuBr, ZnSand ZnSe; the transition metal ion is selected from the group consistingof Cu²⁺, V³⁺, V⁴⁺, Ti³⁺, Ni²⁺, Co²⁺, Fe²⁺, Fe³⁺, Mn²⁺, Mn³⁺, Cr³⁺, Cr⁶⁺and Mo⁴⁺; the rare earth ion is selected from the group consisting ofPr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Sm²⁺ and Eu²⁺; and theanion is selected from the group consisting of OH⁻, O₂ and F⁻.
 3. Amethod of fabricating an optical waveguide array, which comprises thesteps of: providing a glass containing one or more of absorbingmaterials with characteristic absorption in a wavelength region for thevisible range, said absorbing materials being selected from the groupconsisting of metal microparticles, semiconductor microparticles,transition metal ion, rare earth ion and anion; irradiating said glasswith a pulsed laser beam with an energy sufficient to induce change of arefractive index as well as decrease of characteristic absorption insaid wavelength region for the visible range, in the manner such that afocal point of said pulsed laser beam is preset in an inner part of saidglass; relatively shifting said focal point in the inner part of saidglass to form a continuous domain where change of a refractive index aswell as decrease of characteristic absorption in said wavelength regionfor the visible range occur; relocating said focal point; and repeatingthe irradiation with said laser beam to form a plurality of waveguidesin the inner part of said glass.
 4. The method of fabricating an opticalwaveguide array as claimed in claim 3, wherein the metal microparticlesare selected from the group consisting of Au, Ag, Cu and Pt; thesemiconductor microparticles are selected from the group consisting ofCdS, CdSe, CdTe, CuCl, CuBr, ZnS and ZnSe; the transition metal ion isselected from the group consisting of Cu²⁺, V³⁺, V⁴⁺, Ti³⁺, Ni²⁺, Co²⁺,Fe²⁺, Fe³⁺, Mn²⁺, Mn³⁺, Cr³⁺, Cr⁶⁺, and Mo⁴⁺; the rare earth ion isselected from the group consisting of Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Dy³⁺,Ho³⁺, Tm³⁺, Sm³⁺, and Eu²⁺; and the anion is selected from the groupconsisting of OH⁻, O₂ ⁻ and F⁻.